Glossary

Quick definitions for OpenSpec terminology. For narrative context, see what is SDD? and the workflow page.

Concepts

Spec-driven development (SDD): Maintaining durable specs (proposals, requirements, design) in the repository so humans and AI tools share the same source of truth.
Change: A unit of work represented as a folder under openspec/changes/<name>/ with planning artifacts and optional implementation notes.
Spec delta: The set of differences a change introduces to requirements or behavior, often easier to review than a raw code diff alone.

/opsx:new <slug>: Creates a new change directory and begins the proposal flow.
/opsx:ff: “Fast-forward”: generate planning documents (proposal, specs, design, tasks) in one pass when you are ready.
/opsx:apply: Instructs the assistant to implement work according to the current change’s tasks and specs.
/opsx:archive: Moves a completed change into archive and reconciles long-lived specs.

proposal.md: Why the change exists, what is in scope, and key decisions at a product/engineering level.
specs/: Requirements and scenarios—often the behavioral contract for the change.
design.md: Technical approach: components, data flow, migration steps, and tradeoffs.
tasks.md: Ordered checklist of implementation steps; primary driver for /opsx:apply.
AGENTS.md: Instructions tuned for AI assistants working in this repository (conventions, commands, guardrails).
openspec/changes/archive/: Historical changes kept for traceability after archiving.

OpenSpec CLI: The @fission-ai/openspec npm package; installs global commands such as openspec init.
MCP server: Optional Model Context Protocol integration so compatible clients can load OpenSpec context programmatically. See MCP integration.